The present invention relates to an apparatus for drying the disk-shaped ends for beverage and food cans and, more particularly, to an improved apparatus of the type in which a continuous stack of can ends is fed through a drying chamber and caused to traverse a serpentine path while heated drying air is blown across the moving line of can ends.
Can ends for beverage and food cans are typically made of aluminum or steel and, in either case, are provided with a downturned peripheral lip which is crimped over the open end of a cylindrical can body in a seaming operation to close the container. A coating of a sealing compound is applied to the annular lip and the compound must be dried and cured before the end is attached to the can body. With the advent of water-based sealing compounds, extended drying times have been required. One particularly satisfactory apparatus for drying can ends is disclosed in U.S. Pat. No. 4,333,246. In the device disclosed in this patent, the drying oven includes a pair or pairs of rails, each forming a serpentine track which supports a line of can ends disposed in face-to-face relation for movement along the track through a drying chamber in which a pair of linear nozzles are positioned to direct convergent streams of heated drying air against the line of moving can ends. As the line of can ends traverses the horizontal curves defined by the serpentine track, the edges of the cans fan and separate slightly, allowing penetration of the drying air streams between adjacent can ends. A special feature of this prior art device orients the drying air nozzles so that over at least a portion of the serpentine track, the air streams impinge tangentially against the can ends, causing them to rotate as they move along the track through the oven. The device was designed particularly to dry relatively small diameter aluminum can ends for aluminum beverage cans which are typically provided with a pronounced edge flange. It is believed that this construction enhances the ability of the prior art can end drying ovens to cause some rotation of the can ends as they pass through the drying chamber.
Steel can ends used more commonly for food cans, on the other hand, are typically larger in diameter and somewhat flatter because they do not include as deep an edge flange as aluminum beverage can ends. As a result, steel can ends tend to stack more tightly together, and do not readily separate as they traverse the serpentine track of the drying oven disclosed in the above identified U.S. Pat. No. 4,333,246. As a result, insufficient or uneven drying of the sealing compound in steel food can ends has resulted. As the diameters of steel can ends increase, the problem tends to become worse. Typical aluminum beverage can ends are about 21/8" (5.4 cm) in diameter. The heavier steel food can ends are made in a large number of diameters, common diameters being 3" to 47/16" (7.6 to 11.3 cm).